1. Field of the Invention
The present invention relates to an access network system, and in particular to an access network system (subscriber line transmission system) having a test function for performing a maintenance management of an access line (subscriber line).
In recent years, data communication and the like using an access line have been generally utilized. Performing a maintenance management of such an access line during communication without any disconnection is important for realizing a high quality service in the communication.
2. Description of the Related Art
A conventional PSTN (Public Switched Telephone Network) access network system has used only on/off-hook (loop open/close) information of a user or subscriber terminal (telephone) as information for grasping a line or circuit availability status of a PSTN user.
Since an access line assumes a loop close status also in case of short-circuit for some fault, it has been impossible to determine whether the loop close status is due to the fault or a mere off-hook.
When testing the access line which is the off-hook (loop close) state, it has been required that a maintenance person regards that the line is busy and can not be tested, and retries a test when the access line assumes the on-hook (loop open) state.
When determining the line in the off-hook state to be abnormal, the maintenance person has been required to compulsorily test the access line and to determine whether the abnormality is due to a mere off-hook state or the above-mentioned short-circuit.
On the other hand, since a conventional ISDN (Integrated Services Digital Network) access network system has no factor for grasping a physical line status by the method, it has no means for determining whether the user actually uses the line or the fault occurs in the line when the line is busy.
Therefore, the maintenance person has suppressed transmitting and receiving calls by manually changing the mode of the access line to a maintenance mode to test the access line.
As mentioned above, in the conventional access network systems, the PSTN access line has been compulsorily tested by the maintenance person""s determination, while the ISDN access line has been tested with being compulsorily switched over to the maintenance mode. Accordingly, even when the line is used without problems, a damage can occur such that the line is disconnected during conversation or data communication.
It is accordingly an object of the present invention to grasp an availability status of an access line to be tested in an access network system which performs a maintenance management of the access line.
In order to achieve the above-mentioned object, an access network system, according to claim 1, of the present invention comprises; a processor for performing a connection and a release process of a bearer channel and storing an allocation status of the bearer channel to be managed, and a system manager for determining an availability status of an access line based on the allocation status.
FIG. 1 shows an access network system 20 and a local exchange (switchboard) 30 operated by e.g. the V5.2 interface. The access network system 20 and the local exchange 30 are respectively composed of a physical layer in the layer 1, a data link layer in the layer 2, and e.g. BCC (Bearer Channel Connection) protocol entities (processors) 22, 32, system managers 25, 35, and resource managers 27, 37 in the layer 3. The local exchange 30 further has a PSTN/ISDN protocol entity 38 in the upper layer.
The BCC protocol entities 22 and 32 of the access network system 20 and the local exchange 30 mutually transmit/receive the messages of the BCC protocol prescribed at a V5.2 interface point according to a predetermined procedure when a user calls or is called, thereby connecting and releasing the bearer channel.
The processor 22 in the access network system 20 of the present invention stores and manages the allocation status of the bearer channel. The system manager 25 determines whether the availability status of the access line is xe2x80x9cbusyxe2x80x9d when the allocation status of the bearer channel is xe2x80x9cbeing allocatedxe2x80x9d. Thus, it becomes possible to grasp the availability status of the access line.
Also, in the present invention according to claim 2, the processor 22 may determine the allocation status based on an ALLOCATION COMPLETE message and a DE-ALLOCATION COMPLETE message for the bearer channel.
Namely, the processor 22 can determine that the bearer channel is allocated by the xe2x80x9cALLOCATION COMPLETE messagexe2x80x9d of the bearer channel or that the bearer channel is released (not allocated) by the xe2x80x9cDE-ALLOCATION COMPLETE messagexe2x80x9d, which are stored as the allocation status.
Thus, it becomes possible to easily grasp the allocation status of the bearer channel.
Also, in the present invention according to claim 3, the access line may form a PSTN.
Thus, the availability status of the PSTN access line can be grasped.
Also, in the present invention according to claim 4, the access line may form an ISDN-BRA (Basic Rate Access), i.e. N-ISDN.
Thus, the availability status of the ISDN-BRA access line can be grasped.
FIG. 2 shows a V5.2 protocol sequence in which a PSTN user terminal 10 calls a terminal 40 through the access network system 20 and the local exchange 30 connected by e.g. the V5.2 interface.
Messages M1-M9 transferred between the access network system 20 and the local exchange 30 are protocol messages of the V5.2 interface prescribed by ETS300 324-1/300 347-1 of the ETSI (European Telecommunication Standard Institute) when the PSTN user calls.
Receiving an off-hook signal indicating a call originated from the user terminal 10 (at step S1), the access network system 20 exchanges an xe2x80x9cESTABLISH message M1xe2x80x9d and an xe2x80x9cESTABLISH ACK message M2xe2x80x9d with the local exchange 30.
After this exchange, the local exchange 30 transmits an xe2x80x9cALLOCATION message M3xe2x80x9d instructing the allocation of the bearer channel to an address (L3 address) of the layer 3, while the access network system 20 returns an xe2x80x9cALLOCATION COMPLETE message M4xe2x80x9d instructing that an allocation process is normally executed.
The local exchange 30 sends a dial tone (at step S2), so that the user terminal 10 can perform dialing (SIGNAL of 1st digit-last digit) (at step S3).
After ringing, the local exchange 30 returns a ringing back tone to the terminal 10. When the called terminal 40 sends an off-hook signal to the local exchange 30 (at step S4), conversation is started and ended with an on-hook signal (at step S5).
The access network system 20 which has received the on-hook signal transfers a SIGNAL (on-hook) message M5, a DE-ALLOCATION message M6, a DE-ALLOCATION COMPLETE message M7, a DISCONNECT message M8, and a DISCONNECT COMPLETE message M9 to/from the local exchange 30 to de-allocate or release the bearer channel.
Namely, the bearer channel is allocated to the user terminal 10 having originated calls, which is held during the communication.
Accordingly, it becomes possible to grasp the availability status of the user terminal 10 by storing the allocation status of the bearer channel for every user terminal 10.
FIG. 3 shows a V5.2 protocol sequence in which an ISDN user terminal 10 connected by e.g. the V5.2 interface calls the terminal 40 through the access network system 20 and the local exchange 30.
Messages M11-M35 transferred between the access network system 20 and the local exchange 30 are prescribed by the above-mentioned ETS300 324-1/300 347-1.
The messages M19, M22-M26, and M29 are the ones of the ISDN user-network protocol (DSS-1: Digital Signaling System No.1).
The abbreviations within the parentheses of the messages M17, M18, M22-M26, and M29 respectively stand for as follows:
SABME: Set Asynchronous Balanced Mode,
UA: Unnumbered Ack,
CALL PROC: Call Proceeding,
ALERT: Alerting,
CONN: Connect,
DISC: Disconnect,
REL: Release,
RELCOM: Release Complete.
The messages M20, M21, M27, and M28 are respectively the same as the messages M3, M4, M6, and M7 shown in FIG. 2. They are the messages relating to the allocation status (allocation/de-allocation) of the bearer channel. It is to be noted that the messages M11-M19, M22-M26, and M29-M35 are added as the messages of the above-mentioned prescript, which will not be described hereinafter.
Accordingly, it becomes possible to grasp the availability status of the user terminal 10 by storing the allocation status of the bearer channel for every ISDN user terminal 10.
FIG. 4 shows a V5.2 protocol sequence in which the PSTN user terminal 10 is called by the terminal 40.
Also when the user terminal 10 is called, the BCC protocol messages instructing the allocation/de-allocation of the bearer channel are exchanged between the local exchange 30 and the access network system 20. An xe2x80x9cALLOCATION message M41xe2x80x9d in FIG. 4 is the protocol message instructing the allocation of the bearer channel to the L3address to be called. An xe2x80x9cALLOCATION COMPLETE message M42xe2x80x9d is the message notifying that the allocation process is normally completed.
Also, when the bearer channel is de-allocated, the same messages (not shown) as the xe2x80x9cDE-ALLOCATION message M6xe2x80x9d and the xe2x80x9cDE-ALLOCATION COMPLETE message M7xe2x80x9d shown in FIG. 2 are exchanged.
Accordingly, even at the time of signal arrival, it becomes possible to grasp the availability status of the PSTN user terminal 10 by storing the allocation status of the bearer channel for every user terminal 10.
FIG. 5 shows a V5.2 protocol sequence in which the ISDN user terminal 10 is called by the terminal 40. It is to be noted that messages M51-M56 and M59-M65 do not relate to the present invention, so that their description is hereby omitted.
Also in this sequence, an xe2x80x9cALLOCATION message M57xe2x80x9d instructing the allocation of the bearer channel, an xe2x80x9cALLOCATION COMPLETE message M58xe2x80x9d, the xe2x80x9cDE-ALLOCATION messagexe2x80x9d instructing the de-allocation, and the xe2x80x9cDE-ALLOCATION COMPLETE messagexe2x80x9d (not shown) are exchanged between the local exchange 30 and the access network system 20.
Accordingly, even at the time of signal arrival, it becomes possible to grasp the availability status of the ISDN user terminal 10 by storing the allocation status of the bearer channel for every user terminal 10.
Also, in the present invention according to claim 5, the system manager may further determine the availability status based on loop open/close information of the access line.
Namely, the system manager can determine the availability status of the access line based on the allocation status of the bearer channel and the loop open/close (on/off-hook) status of the PSTN user circuit.
This will be described referring to an availability status table shown in FIG. 6 for determining the availability status of the access line based on the bearer channel allocation status and the loop open/close status of the PSTN access line by the BCC protocol.
Availability statuses xe2x80x9cIdlexe2x80x9d, xe2x80x9cBusyxe2x80x9d, xe2x80x9cLockoutxe2x80x9d, and xe2x80x9cBusy (Ringing)xe2x80x9d are set corresponding to four groups whose BCC protocols and loop statuses are respectively {circle around (1)} xe2x80x9cDe-allocationxe2x80x9d and xe2x80x9cOpenxe2x80x9d, {circle around (2)} xe2x80x9cAllocationxe2x80x9d and xe2x80x9cClosexe2x80x9d, {circle around (3)} xe2x80x9cDe-allocationxe2x80x9d and xe2x80x9cClosexe2x80x9d, and {circle around (4)} xe2x80x9cAllocationxe2x80x9d and xe2x80x9cOpenxe2x80x9d.
Namely, the availability status of the access line can be classified into four statuses i.e. xe2x80x9cIdlexe2x80x9d, xe2x80x9cBusyxe2x80x9d, xe2x80x9cLockoutxe2x80x9d, and xe2x80x9cBusy (Ringing)xe2x80x9d.
Thus, it becomes possible to more precisely grasp the availability status of the user terminal 10.
Also, in the present invention according to claim 6, a test unit for testing the access line may be further provided based on the availability status.
Namely, when testing the access line, the test unit can test the access line which is not xe2x80x9cbusyxe2x80x9d by referring to the availability status corresponding to the access line concerned.
Thus, it becomes possible to test the access line without disconnecting the line during the conversation or the data communication.
Also, in the present invention according to claim 7, the test unit may test a plurality of access lines, and select the access line which can be tested based on the availability status of each access line to autonomously test the access line.
Furthermore, in the present invention according to claim 8, the test unit may test the access line which has not yet been tested when the access line becomes possible to be tested.
Namely, the test unit which tests a plurality of access lines sequentially selects the access line to be tested, and tests the access line which is not xe2x80x9cbusyxe2x80x9d by referring to availability status information of the selected access line. The test for the access line in the state of xe2x80x9cbusyxe2x80x9d is awaited until the access line becomes not xe2x80x9cbusyxe2x80x9d, or is retried by referring to the availability status after all of the access lines to be tested in the state of not xe2x80x9cbusyxe2x80x9d have been tested.
Thus, it becomes possible to efficiently test a plurality of access lines without disconnecting the line during the conversation or the data communication.